VLSM Calculator
Enter your network address and define multiple subnets with different host requirements to calculate an efficient VLSM allocation plan. Get optimized variable-length subnet masks, network addresses, broadcast addresses, and usable host ranges for each subnet — maximizing IP address utilization across your network. Use the tool to calculate cidr for point-to-point links — /30 and /31 blocks with their exact host ranges.
Network Configuration
Allocation Summary
What is VLSM?
Variable Length Subnet Mask (VLSM) allows you to use different subnet masks for different networks within the same address space. This results in more efficient IP address allocation compared to classful networking or fixed-length subnet masks.
VLSM works by allocating larger subnets first, then filling in the remaining space with smaller subnets. This "best fit" approach minimizes wasted IP addresses.
Related Network Tools
Explore these related tools for subnet calculation and IP address management. The ipv4 to ipv6 converter converts any IPv4 address to the IPv4-mapped IPv6 notation used in dual-stack socket libraries.
Additional networking calculators for IP address planning and network analysis. Use the visual subnet calculator to explore how different prefix lengths carve up a parent block and visualise address allocation.